Molecular gas laser

ABSTRACT

The closed cycle solid state optically pumped gas hybrid (chemical recovery) system utilizes a laser diode excited solid state, fiber or bulk, laser as a pump for a molecular gas, or gas mix, medium. The existence of efficient high power laser diode excited solid state fiber or bulk lasers, output spectrally matched to suitable principle and excited level 1st and 2nd overtones of relevant gases, is the enabling system technology. The utilization of such in combination with suitable gases introduces a range of viable, in principle sourcing on laser diodes and thus effectively laser diode pumped, gas laser systems with access to the ˜3.5 μm to ˜5.2 μm and ˜9 μm to ˜11 μm spectral region. Continuous wave or pulsed operation, with significant energy capability courtesy of solid state storage, is admitted.

BACKGROUND OF INVENTION

1. Field of invention

This invention relates to high power, infra-red lasers, morespecifically, efficient laser diode excited solid state pumped moleculargas lasers and amplifiers.

2. Description of prior art

Mid-infrared vibrational-rotational transition lasers are well known.They are potentially very important as they have high power/high energycapability within critical atmospheric windows in the mid-wave infrared(MWIR) and long wave infrared (LWIR) spectral regions. These systems aretypically energized using chemical interactions or electricaldischarges. Chemically pumped systems are undesirable from thestandpoint of the reactive precursors required, plus toxic exhaustproduct handling or release considerations. Electrical discharge pumpedCarbon Monoxide (CO) lasers are less than successful as they generallyemit at wavelengths greater than ˜5.6 μm which is above the ˜4.6 μm to˜5.4 μm atmospheric transmission window. There is a clear need toreplace chemical or electrical discharge excitation of these devices.

U.S. Pat. No. 7,145,931 (Diode Pumped Alkali-Molecular Lasers andAmplifiers) describes optically-pumped mid-infraredvibrational-rotational transition gas lasers and amplifiers withimproved efficiency and practicality, to wit, inventive lasers andamplifier devices include: laser active media comprising a mixture ofalkali vapor, selected hetero-nuclear molecular gas, and one or morebuffer gases; conventional semiconductor laser diode pump sources withnanometer scale spectral bandwidths; and preferential laser emission inrovibrational transitions among relatively low-lying vibrational levels.

This is a laser diode pumped resonant transfer approach and is deficientfor a number of reasons. It is deficient in that it is not configuredfor direct and selected excitation of higher vibrational levels as thisis a resonant transfer approach, as distinct from the concept proposedherein where multiple principle and excited state overtone pumps areapplied [FIG. 1, A] in an intentional manner. This would have directconsequences in terms of the spectral diversity produced by the systemwhich is directly related to the number of fundamental cascade (v→v−1transitions—[FIG. 1, B]. v is the vibrational level quantum numberdesignator) elements present in lasing. Furthermore, direct pumpspectral location has an influence on cascade formed; that is, it exertsa degree of selection on content of the spectral output. The patentcited is deficient in that any dissociated halogen components derivedfrom v⇄v exchange up pumping will scavenge alkali atomic vaporcomponents via principally three body interactions erodingdonor/acceptor gas mix balance. Recombined diatomic homonuclear halogenswill react with alkali atomic vapor components as M+X₂→X+MX (M is alkalivapor component—X is halogen). Alkali atomic vapor components have theability to enter into M+HX→H+MX, M*+HX→H+MX and M*+HX*→H+MX (HX isacceptor component of U.S. Pat. No. 7,145,931—M is atomic vaporcomponent—X is atomic halogen—* superscript denotes excitation, H isnominal, it may equally well be D) exchange interactions at operationaltemperatures concerned also eroding donor/acceptor gas mix balance. Thelatter issues clearly do not lend themselves to implementation of aclosed cycle gas operating system free of precursor consumption orproduct handling. In addition, the system has to be conditioned foralkali vapor generation—typically in the range of 300K to 500K. It isdeficient in that a laser diode pumped system of this nature lacks theability to function in a pulsed significantly high power/high energymode of operation as the system lacks lasing medium energy storagecapability. This is also distinct from the invention presented herewhich admits a laser diode excited bulk pulsed Tm solid state driver andhas the capability to store and deliver high energy pulse withextraction 4 kJ/liter, plus closed cycle operation of gas component ofsystem which, when in full cascade, merely functions as a throughputdevice with wavelength shift and output proportional to input in fullcascade.

Additionally it has been asserted in the above cited patent (U.S. Pat.No. 7,145,931) that direct optical pumping of molecular transitionsnecessarily results in reduced performance from the pump source systembecause of the need to narrow the line width of these sources to matchthe line width of the molecular transitions concerned. Typically, forthe gas system process presented herein, a rotational-vibrational linewidth will be in the range of 0.5 GHz to ˜2 GHz. This is equivalent to,for the pump concerned, ˜0.007 nm to 0.03 nm. Such interaction linewidths do traditionally diminish solid state laser performance courtesyof the limitations of cross relaxation. However, the cited patent'sassertion is deficient as this problem is amenable to the followingmitigating features particular to this invention: (a) The specific fullsustained cascade process, in a suitable gas optically pumped, can onlyarise for pump pulse durations significantly greater than several tomany times the rotational manifold thermalization time constant of thepumped gas. Typically this implies optical pump durations greater thanseveral hundred nanoseconds. Thus short pulse interactions are notsuitable and not under consideration and thus the rapid cross relaxationin highly Tm doped YAG (Yttrium Aluminum Garnet), for example, inconjunction with its long excited state lifetime of ˜10 ms will allowfor efficient narrow band extraction. Similarly cross relaxation inTm:glass, as in fibers, is also rapid at high dopant levels. Solid stateTm doped pulsed systems tend to produce, or can be configured toproduce, pulse lengths in the range desired which is greater thanseveral hundred nanoseconds to microseconds; a case with Ceramic Tm:YAGhas recently been demonstrated, the implication of which is thatarbitrarily configured and scaled highly doped amplifier structures canbe fabricated. (b) In the case of continuous wave (CW) fiber pumps, themedium is characterized by an inhomogeneously broadened gaindistribution. It is possible to amplify several spectrally separatewavelength components in such a medium—enhancing the effectiveinteraction bandwidth and thus system performance. This fact has naturalsynergism with the principle plus multi excited state overtone or multiprinciple overtone (differing rotational vibrational transitions) gaspump feature of the invention presented here. To a degree this behaviorwould also manifest for pulsed Tm:YAG, or YAP, YSGG or any othersuitable solid state host, as system is quasi 4 level with differentwavelengths between differing Stark components of the energy levelstructure and in response, inhomogeneously broadened.

This approach is also deficient, in regards of output spectral rangeaccessible and thus for specific applications, in terms of the fact thatresonant transfer systems in general (and as stated in the abstract(Krupke: U.S. Pat. No. 7,145,931)) offer preferential laser emission inro-vibrational transitions among relatively low-lying vibrationallevels. This as indicated will limit the spectral diversity achievableby pumping of higher vibrational levels which is directly addressableand may be intentionally tailored within the context of the inventionpresented here.

The article, CW Optical Resonance Transfer Lasers. [J. H. S. Wang et al,Journal de Physique, Colloque C9, supplement au n° 11, Tome 41, 1980,C9-463] describes wavelength-agile, single and multiline laser radiationthat has been obtained from a subsonic gas flow system which isoptically pumped with a multiline chemical laser. This optical resonancetransfer laser (ORTL) concept was first demonstrated on the 10.6 μmDF/CO₂ system in 1976. Since then, several infrared (IR) laser pumpedmolecular lasers have been demonstrated. The pump laser is either a CW(Continuous Wave) HF or DF chemical laser. Two classes of ORTL have beendeveloped: inter- and intramolecular ORTLs. The demonstratedintermolecular systems include: 10.6 μm DF/CO₂, 10.8 μm DF/N₂O, 4.1 μmDF/HBr, 3.8 μm HF/DF and 3.85 μm HF/HCN. The intramolecular ORTLsinclude 2.9 μm HF/HF and 3.9 μm DF/DF. Demonstration experiments and thekinetics of ORTL systems will be described.

This was a fundamental cascade optically pumped followed by afundamental cascade lasing response system. The approach of this articleis deficient as there is no practical value to optically pumping HF withanother HF laser. That is, there is no useful wavelength shift inducedbetween pump input and output. The approach of this article is alsodeficient in that the pump chemical HF laser system utilized isimpractical. Chemical lasers although in general efficient requireexhaust product plus precursor fuel and oxidizer handling. If purelycold reaction discharge initiated by dissociation of halogen donor, thenare typically inefficient plus still require product gas handling andhigh voltage.

The article, CW Optically Resonance Pumped Transfer Laser in DF-CO₂System [J. H. S. Wang et al, Applied Physics Letters, 31(1), 1977,35-37] describes an optically pumped CW 10.6 μm DF/CO₂ transfer laserthat has been demonstrated. This has been accomplished by exciting a 3cm×0.3 cm transfer laser medium, consisting of a 1:19:80 DF/CO₂/Heflowing gas mixture at 22 Torr and room temperature, with a 70 Wattmultiline chemical DF laser. In the preferred ‘intracavity’configuration where the transfer-laser medium was located in between theDF-laser resonator mirrors, 1.5 W of 10.6 μm power was out coupled. Thispower corresponds to a photon conversion efficiency of available DF-pumpflux to out coupled transfer-laser flux of 6%. Analysis predicts thatmultiline DF laser-to-single-line CO₂ photon conversion efficienciesexceeding 90% should be attainable in an optimized apparatusconfiguration.

This approach is deficient in that the pump laser is impractical.Chemical lasers although in general efficient require exhaust productplus precursor fuel and oxidizer handling. If purely cold reactiondischarge initiated by dissociation of halogen donor, then are typicallyinefficient plus still require product gas handling and high voltage.

The article CW HF/HCN and HF/DF Optical Resonance Transfer Lasers [J.Finzi et al, IEEE Journal of Quantum Electronics, QE-16(9), 1980,912-914] describes that CW laser oscillation has been observed in HCN at3.85-3.9 μm and in DF at 3.8-4.0 μm. Mixtures of HF/HCN/He and HF/DF/Hewere irradiated by a CW multiline HF chemical laser. Vibrationalexcitation of HF by resonance absorption, followed by rapid v-v energytransfer to HCN or DF, produced a population inversion. The HCN gain wasestimated to be between 0.08 and 0.17 percent/cm. The DF gain wasgreater than 0.17 percent/cm and 25 mW of power were out coupled.

This approach is deficient in that the pump laser is impractical.Chemical lasers although in general efficient require exhaust productplus precursor fuel and oxidizer handling. If purely cold reactiondischarge initiated by dissociation of halogen donor, then are typicallyinefficient plus still require product gas handling and high voltage.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide for an efficient,at system electrical interface, laser diode excited Continuous Wave (CW)or quasi CW and pulsed energy capable, highly multispectral MWIR to LWIRlaser system overcoming the shortcomings of prior art devices. Theinvention presented here is to use the synergism inherent in the recentdevelopment of efficient high power/high energy laser diode pumpedThulium (Tm), or Erbium (Er), doped solid state lasers and the matchingof said systems useful spectral range with 1^(st) (principle and excitedstate [FIG. 1, A], or multiple principle), or 2^(nd), overtonetransitions of suitable relevant gases. Several spectrally discretepumps on distinct transitions of a specific overtone are also possible[analogous with pump on [FIG. 4, A]]. Melded with a gas component andimplemented appropriately this has the ability to initiate a sustainedfundamental transition lasing cascade from near the highest vibrationallevel excited by the pump geometry selected to the molecular groundvibrational level. The issue of pump driven dissociation, whereapplicable, is addressed by appropriate biasing of system operating gasmix to favor hot reaction reconstitution to an excited state of theactive gas mix component. The latter resulting in a closed cyclechemically related photonic energy contribution to the fundamentaltransition lasing process. Globally a closed cycle gas operating systemis engendered wherein the optically pumped gas mix recovery is toessentially preset conditions without any requirement for precursor orproduct gas handling. In the case of active gas components withpermanent and significant dipole moments far infra red amplifiedspontaneous emission may be leveraged to minimize thermal shedding ingas when appropriately configured.

This system is absent primary chemical or discharge pumping, and is thenabsent the related fuel or exhaust product gas handling issues. Spectralagility is inherent in rotational manifold relaxation rates admittingefficient channeling of broadly multispectral output into desiredatmospheric windows, or of output into atmospheric windows, or indeedinto a near single frequency output comprised of multiplefundamental-transition cascade elements within atmospheric windows.

Implementation of multiple overtone pumps enhances interaction bandwidthwith laser diode pumped solid state source (Tm or Er doped—any suitablesolid state host) and thus optimizes efficiency of that systemcomponent, and thus of system globally.

Implementation of multiple, principle plus excited state, overtone pumpswill permit selection of long wavelength edge of fundamental cascadeoutput spectral range. Implementation of overtone pumps ensures a usefulpump to output wavelength shift.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated into and form a partof the disclosure, illustrate embodiments of the invention, and togetherwith the description, serve to explain the principles of the invention.

FIG. 1: Multiple principle and excited state overtone pump concept (A).This broadens bandwidth of interaction with laser diode solid statecomponent of system enhancing said systems performance. Fundamentalground return lasing cascade follows for medium appropriately located ina suitably broadband resonator (B).

FIG. 2: One or more temporally synchronized laser diode pumped solidstate oscillators, spectrally discrete but individually locked ontodesired principle and excited state overtone pumps (A). Spectrallycombined (B) they provide for adequately broadband interaction withlaser diode pumped solid state amplifier to yield enhanced efficiency(C). Amplifier output introduced into gas component resonant cavity in amanner to optimize matching between pumped volume and cavity definedlasing mode volume (D). Gas component lasing output (E).

FIG. 3: Functionally identical to FIG. 2, but with fiber as opposed tobulk systems.

FIG. 4: Multiple principle overtone pumps in this case (A). Multiplepumps spectrally discrete and such that they constitute an adequatebandwidth for effective laser diode pumped solid state systeminteraction and thus efficiency. Low energy defect between H¹³CN (donor)and CO (acceptor) results in rapid (B) near resonant excitation transferto the CO molecule (C). Subsequent cascade lasing of CO molecule (D). HIto CO donor acceptor plus pump functional arrangement would be similar.

FIG. 5: Example of projected Quasi CW behaviour in HCl driven into fullcascade by a principle and excited state overtone pump configuration.Conversion efficiency of this element ˜87% (output power to absorbedpower). Optical pump absorbed ˜1200 W.

DETAILED DESCRIPTION OF INVENTION

Definition of Deactivant or de-activant: a molecule or atom which may ormay not efficiently serve to accept or dissipate excitation from anotherexcited molecule, thus deactivating said molecule.

The invention presented here is to use the synergism inherent in therecent development of efficient high power/high energy laser diodepumped Thulium (Tm) doped solid state lasers and the matching of saidsystems useful spectral range with 1^(st) (principle and excited state[FIG. 1, A], or multiple principle), overtone transitions of suitablerelevant gases. Several spectrally discrete pumps on distincttransitions of a specific overtone are also possible [analogous withpump on [FIG. 4, A]—distinct rotational vibrational transitions].

This multi spectral pump approach broadens the interaction bandwidthexperienced by the solid state pump sources significantly above that ofthe typical single frequency narrow band matched to a single moleculartransition approach, optimizing the efficiency of the solid state pumpcomponent of the system.

In addition, the identified methodology leverages a behaviorcharacteristic of said gases, admitting a full sustained fundamentaltransition lasing cascade from more or less pump terminal level toground (v→v−1→v−2 and so on [FIG. 1, B]) when overtone pumped, orcascade overtone pumped. This arising under appropriate pumpingconditions and admitting broadly multispectral output. Principle denotesout of ground pump overtone transition (0→2 for example, [FIG. 1, A]),excited state denotes an overtone pump transition originating out of anyexcited vibrational level (v→v+2, [FIG. 1, A]).

Relevant gases are HCl, DF, HBr and by association CO₂ if desired. CO₂is pumped via resonant transfer as per: HBr*+CO₂→HBr+CO₂*—reactions suchas HCl*+CO₂→HCL+CO₂* and DF*+CO₂→DF+CO₂* represent the preferredembodiments of the resonant transfer methodology as the transitionenergy defect is minimized at high vibrational quantum number resultingin quenching of collisional mediated vibrational up pumping of donorspecies. The * superscript denotes excitation.

Solid state Er doped (Yb co-doped, as required, or other codopant)system spectral output overlays overtone transitions of other relevantgases. Said relevant gases are HI (2^(nd) overtone) and HCN(0000->0002—a 1^(st) overtone). HI and HCN will also function as donorsin resonant transfer arrangements with CO. That is to say:H¹³CN*+CO→H¹³CN+CO* or HI+CO→HI+CO* in both cases of which the defect isless than or equal to background thermal kT.

In the case of resonant transfer systems spectral output may derive fromboth species—directly pumped donor and acceptor as determined by thecomponent partial pressures and pump conditions.

Buffer gas components such as He, Argon, H₂, N₂ to be implemented asrequired.

In the case of hydrogen halide/deuterium halide, presence, the gascomponent would be biased with the related molecular halogen to yieldchemical system energy recovery from up pumping driven dissociation plusclosed cycle gas function. Closed cycle gas function, as understoodhere, specifically denotes the preservation of gas mix features, asrecovery is to the initial specification, within some small acceptablevariance. Molecular halogens are ineffective excitation deactivants andthus are tolerable at a significant partial pressure presence in systemgas mix, which favors hot reaction scavenging of atomic hydrogen ordeuterium dissociation products via reactions of the form: H+X₂→X+HX*,which contribute to lasing and thus represent systemic recovery ofuseful energy. Utilization of H is merely for purposes of example, D isequally valid. Activation energies for the H+X₂→X+HX* reactions aremodest, resulting in favorable rates. Thus the optically pumpeddissociation/recovery process is ultimately closed cycle as: M+HX(dissociation band)+X₂→M+X+H+X₂→M+2X+HX*→M+X₂+HX+(lasing cascadephotons) (M=generally any molecular or atomic collision partner). Toreiterate, closed cycle gas function denotes specifically that the gasspecifications, post recovery, are the same as initial specificationswithin some small acceptable variance.

Atomic halogen recombination rates (3 body process typically) thusrepresents the gas mix recovery systemic limiting factor. Simply operatesystem pulsed or quasi CW with adequate inter event timescale forrecovery, alternatively implement gas flow.

At the simplest possible gas process level, with HCl as an example, HClis optically pumped on a principle 1^(st) overtone−v(0→2), plus severalsubsequent excited state 1^(st) overtones such as v(1→3), v(3→5) and soon to the extent desired or possible [FIG. 1, A]. Several spectrallydiscrete pumps on distinct transitions of a specific overtone are alsopossible [analogous with pump on [FIG. 4, A]]. For adequate drivefluence or irradiance the gas medium is driven into a saturationcondition level to level supportive of positive fundamental transitiongain and cascade lasing to ground (v→v−1→v−2 and so on). This is aninherently effective process offering high quantum efficiency withspectral agility as a result of rapid population redistribution withinthe rotational manifolds. FIG. 5 represents a projection of suchbehavior to the multiple overtone pump fundamental cascade lasing schemeof a gas.

As indicated a contributory component to enabling this approach is therecent appearance of highly efficient high power laser diode pumped Tm,or Er, doped solid state systems. Tuning spectral range of Tm solidstate laser systems extends from ˜1.74 μm to ˜2.017 μm. Correspondenceof this spectral range with 1^(st) overtone transitions, principle andexcited state, of HCl, DF and HBr is good. In the case of Er (perhaps Ybco-doped) matching with HCN and HI 1^(st) and 2^(nd) overtonesrespectively is equally good.

The H₁₃CN isotopologue is of particular interest courtesy of itsfacility for near resonant transfer to CO. HI presents with similarcapability, although a full fundamental cascade to ground process,lasing potential in vicinity of ˜4.7 μm to ˜5.2 μm of this molecule isalso viable and of interest. Exchange reactions between CO and HCN, HIor I₂ in mixes are improbable.

This general approach results in what effectively is a laser diodeinitiated/sustained/pumped efficient high power access to the MWIR andLWIR spectral regions via the identified hetero-nuclear and triatomicmolecules identified. The highly efficient Tm doped solid state bulk orfiber laser (or Er doped solid state) is the molecular pump source. Thisapproach is enabled by leveraging cascaded overtone pumping (or multipleprinciple overtone pumping on related rotational vibrationaltransitions, or multiple principle and multiple excited state) of gas toproduce a useful Stokes shifted output in a fundamental transitioncascade to ground (FIG. 5, FIG. 1). The fundamental ground returncascade onset and maintenance is dependent on the achievement, orbetter, of specific threshold optical pump conditions for the moleculargas concerned. The resultant molecular output may be broadlymultispectral or near single frequency. The pump geometry implementedhas a direct bearing on the selection of the long wavelength edge of thefundamental cascade output spectral range produced. The correspondingexistence of matching, spectrally to identified gases, laser diodeexcited solid state pumping technology from which extraction isoptimized by the cascade pump enabled bandwidth enhancement attributableto the methodology presented, and the introduction of chemical photonicrecovery from dissociation products with associated closed cycle gas mixoperation, results in a flexible and sensible system.

For efficient full cascade lasing operation, the pump fluence orirradiance must be such as to override gas vibrational and other lossprocesses sufficiently, with events of sufficient temporal extent, toinduce the requisite pump transition saturation for vibrational levelswhich are essentially rotationally thermalized and positive gain for thefundamental transitions, in a cascade to ground, is the result.

At the gas component level, overtone transition cross sections generallyincrease with source level vibrational quantum number which facilitatesthe effectiveness of pump coupling with diminishing excited levelpopulations. Similarly, in general, fundamental transition crosssections increase with increasing vibrational quantum number to somepoint aiding formation of lasing cascade

The following is a description of the best mode contemplated by theinventor of the laser diode excited solid state optically pumpedmolecular laser with chemical reaction recovery system. A laser diodeexcited, Tm doped, solid state CW laser, comprised of seed fiberoscillators tuned and locked onto principle and excited state overtonefrequencies of gas. Solid state laser element in principle an oscillatoramplifier configuration, amplifier amplifying one or more distinctfrequencies with spectral beam combination prior to amplifier. Amplifieroutput coupled as input into gas component region and matched to volumeof related cavity or waveguide mode. In coupling by spectral beamcombination (a significant wavelength difference exists between pump andgas component output), dichroic optics or any other means. Gas mix asrequired plus bias for chemical reaction recovery. Refer to [FIG. 3, A,B, C, D].

The following is a description of an alternative embodiment contemplatedby the inventor of the laser diode excited solid state optically pumpedmolecular laser with chemical reaction recovery system. A laser diodeexcited, Tm doped, solid state pulsed laser, comprised of seedoscillators tuned and locked onto principle and excited state overtonefrequencies of gas. Solid state laser element in principle an oscillatoramplifier configuration, amplifier amplifying one or more distinctfrequencies with spectral beam combination prior to amplifier.Oscillator outputs temporally synchronized. Amplifier output coupled asinput into gas component region and matched to volume of related cavityor waveguide mode. In coupling by spectral beam combination (asignificant wavelength difference exists between pump and gas componentoutput), dichroic optics or any other means. Gas mix as required plusbias for chemical reaction recovery. Refer to [FIG. 2, A, B, C, D].

The following is a description of an alternative embodiment contemplatedby the inventor of the laser diode excited solid state optically pumpedmolecular laser with chemical reaction recovery system. A laser diodeexcited, Tm doped, solid state quasi CW laser, comprised of seed fiberoscillators tuned and locked onto principle and excited state overtonefrequencies of gas. Solid state laser element in principle an oscillatoramplifier configuration, amplifier amplifying one or more distinctfrequencies with spectral beam combination prior to amplifier.Oscillator outputs temporally synchronized. Amplifier output coupled asinput into gas component region and matched to volume of related cavityor waveguide mode. In coupling by spectral beam combination (asignificant wavelength difference exists between pump and gas componentoutput), dichroic optics or any other means. Gas mix as required plusbias for chemical reaction recovery. Refer to [FIG. 3, A, B, C, D].

As a system feature, if laser diode excited solid state component ofsystem is pulsed or quasi CW, then said system must be such thatresultant event durations are of sufficient temporal extent and in gashybrid component fluence (or irradiance) is sufficient to attain orexceed the required gas pump saturation condition consistent withestablishment of positive gain on all fundamental lasing transitions toground. Temporal extent must be significantly greater than gasrotational manifold thermalization times at least.

As a system feature, if laser diode excited solid state component ofsystem is CW, then said system must be such that resultant in gaselement irradiance must be in excess of a threshold condition, relatedto the maintenance of a pump transition saturation condition, associatedwith positive gain on all fundamental lasing transitions to ground.

As a system feature, a gas component (cell) with suitable broadbandcavity resonator optics to access desired range of excited fundamentalcascade transitions of optically pumped gas is required [FIG. 2, D; FIG.3, D].

As a system feature a gas cell of material inert to gas components, orsubject to prior chemical passivation [FIG. 2, D; FIG. 3, D], isrequired. Gas fill of optical pump gas species of interest (HCl, HBr, DFor HI), plus one or more of He, H₂, Argon and X₂ (molecular halogencomponent with X=Cl, Br, F or I). Halogen component biased to favoratomic H+X₂→HX*+X or D+X₂→DX*+X hot scavenging reactions.

As a system feature, a gas cell of material inert to gas components, orsubject to prior chemical passivation [FIG. 2, D; FIG. 3, D], isrequired. Gas fill of donor/acceptor species mix of interest (HBr+CO₂,HCl+CO₂, DF+CO₂, H₁₃CN+CO or HI+CO), plus one or more of Argon, He, N₂,H₂, Br₂, Cl₂, F₂ or I₂ to the extent required.

As a system feature, a gas fill pressure and mix selected to optimizepump coupling, minimize full sustained cascade onset pump irradiancethreshold (requisite driven saturation condition).

As a system feature, a gas cell with windows of inert materials ofadequate spectral transmission range, bulk absorption and thermalconductivity for system duty cycle selected.

As a system feature, if solid state pump system pulsed or quasi CW,pulse full width at half maximum at least greater or equal to severalhundred nanoseconds at pressures of interest.

As a system feature, in bulk pulsed gas systems, gas flow for thermalmanagement plus heat exchanger required. In low to moderate power CW orquasi CW applications diffusion cooling with limited flow or no flowdependent on operational mode. In high power CW applications slabwaveguide geometry with transverse flow and heat exchanger.

In molecules possessed of permanent dipole moments, the collisionalrotational relaxation process may transition to limited far infra red(FIR) rotational-rotational amplified spontaneous emission (ASE) ifadequately pumped and system configuration is supportive. This wouldhave direct consequences in terms of quantum efficiency and limitedthermal shedding in gas component of system.

As a system feature, passive selection of lasing within atmosphericwindows in optically pumped gas component cell/cavity [FIG. 2, D; FIG.3, D] is imposed by the presence of intracavity low gain elements (orsub cells—low gain denotes spectrally selective absorption) comprised offor example ¹²CO₂+¹³CO₂ at several hundred Torr each in an atomic orhomonuclear molecular buffer gas of several atmospheres. Sub cellsarranged so as to not be subjected to near ˜2 μm pump as CO₂ ispossessed of an optical transition in this spectral region—or preciselymatching pump transitions are excluded. The precise component gaspartial pressures and net pressure to be adjusted as required inpractice. Other absorbing molecular species to be implemented ifadvantageous.

The efficient channeling of system optical output into critical infraredatmospheric windows, plus the natural capability for this output to bebroadly multispectral, renders this invention ideal for disruption ofinfra red imaging and tracking systems. Similarly the spectral agilityenabled ability to channel efficient lasing into a near single frequencyoptical output cascade renders this approach promising for legitimatelyeye safe wavelength directed energy applications. Medical laser andremote sensing applications are additionally valid given the spectralbands accessible.

The forgoing description of the invention has been presented forpurposes of illustration and description and is not intended to beexhaustive or to limit the invention to the precise form disclosed. Manymodifications and variations are possible in the light of the aboveteaching. The embodiments disclosed were meant only to explain theprinciples of the invention and its practical application to therebyenable others skilled in the art to best use the invention in variousembodiments and with various modifications suited to the particular usecontemplated.

1. An optically pumped molecular laser system comprised of a principleovertone, or principle and multiple excited state overtones, or multipleprinciple overtones, or multiple principle and multiple excited stateovertone pumps of suitable gases, these pulsed, CW or quasi CW derivedfrom solid state (Thulium doped) systems to induce in gas a full toground sustained lasing cascade with gas mix biased in favor of the hotchemical reaction for atomic H or D scavenging and thus lasing energyrecovery from dissociation products and closed cycle gas function.
 2. Anoptically pumped molecular laser system according to claim 1, whereinthe spectrally discrete pump transitions ensure adequate solid statesystem interaction bandwidth for efficient solid state system function.3. An optically pumped molecular laser system according to claim 1,wherein the gas hybrid component of this arrangement consists ofselected mixes comprising one or more of the gases (HCl, DF, HBr, He,Argon, Br₂, F₂, Cl₂, H₂, D₂) in appropriate combination for desiredoperation and configured for closed cycle functioning and limitedchemical reaction recovery from pump driven dissociation.
 4. Anoptically pumped molecular laser system according to claim 1, whereinthe laser diode excited solid state pump system is comprised of one ormore laser diode pumped solid state master oscillators, tuned and lockedonto desired gas overtone transition(s), mutually temporallysynchronized if pulsed and combined into a common optical axis byspectral beam combination or any other suitable technique.
 5. Anoptically pumped molecular laser system according to claim 1, whereinthe solid state system seed input is introduced as a common optical axismultispectral beam into a laser diode pumped solid state amplifier togenerate output pump powers (irradiances) and temporal events consistentwith the objective of driving the gas into a saturation conditionconsistent with onset and maintenance of a full to ground returnsustained fundamental transition lasing cascade [FIG. 1].
 6. Anoptically pumped molecular laser system according to claim 1, whereinthe output of the solid state amplifier is introduced into the gascomponent resonant cavity by means of spectral beam combiner, dichroicoptics or any other suitable means consistent with criteria formaintenance of a sustained full to ground return fundamental transitionlasing cascade [FIG. 1, B].
 7. An optically pumped molecular lasersystem according to claim 1, wherein intra gas component cavity low gaincell(s), of at least ¹²CO₂+¹³CO₂ at several hundred Torr each in anatomic or homonuclear molecular buffer gas of several atmospheres, willchannel lasing into atmospheric windows with efficiency if required. 8.An optically pumped molecular laser system according to claim 1, whereinintra gas component cavity low gain cell(s) are arranged so as to not besubjected to near ˜2 μm pump as CO₂ is possessed of an opticaltransition in this spectral region—or precisely matching pumptransitions are excluded, and the precise partial pressures and netpressure utilized to be adjusted as required in practice.
 9. Anoptically pumped molecular laser system according to claim 1, whereinwith optically pumped heteronuclear hydrogen or deuterium halides ofpermanent dipole moment the capacity, if adequately pumped, gas mixconfigured and systemically supported by path length and feedback toadmit FIR (far infra red) lasing from rotational manifold relaxationsduring the full to ground fundamental cascade lasing event exists; andsuch additional photonic emission, out coupled, would reduce gas thermalloading.
 10. An optically pumped molecular laser system according toclaim 1, wherein the gas component may alternatively function with theresonant transfer acceptor species CO₂ in donor environment of HBr, HClor DF.
 11. An optically pumped molecular laser system according to claim1, wherein the gas component of the resonant transfer acceptor CO₂arrangement consists of selected mixes comprising one or more of thegases (HCl, DF, HBr, He, Argon, Br₂, F₂, Cl₂, N₂, H₂, D₂, CO₂) inappropriate combination for the desired operation and configured forclosed cycle functioning and limited chemical reaction recovery frompump driven dissociation of hydrogen halide components as required. 12.An optically pumped molecular laser system according to claim 1, whereinthe gas component of the resonant transfer acceptor CO₂ arrangement ifappropriately configured and pumped, admits lasing on both donor andacceptor transitions—or preferentially on acceptor.
 13. An opticallypumped molecular laser system according to claim 1, wherein intra gascomponent cavity low gain cell(s), of a combination of any suitablemolecular species with appropriate spectral absorption structures atrequisite partial pressures and admixed with atomic or molecular buffergas/es of several atmospheres, will channel lasing into atmosphericwindows with efficiency if required.
 14. An optically pumped molecularlaser system comprised of a principle overtone, or principle andmultiple excited state overtones, or multiple principle overtones, ormultiple principle and multiple excited state overtone pumps of suitablegases, these pulsed, CW or quasi CW derived from solid state (Erbiumdoped) systems to induce in gas a full to ground sustained lasingcascade with limited chemical reaction lasing energy recovery and closedcycle gas function in case of hydrogen halide presence.
 15. An opticallypumped molecular laser system according to claim 14, wherein thespectrally discrete pump transitions ensure adequate solid state systeminteraction bandwidth for efficient extraction
 16. An optically pumpedmolecular laser system according to claim 14, wherein the gas componentconsists of either a resonant transfer acceptor species CO in donorenvironment of HI or H¹³CN, or simply HI.
 17. An optically pumpedmolecular laser system according to claim 14, wherein the gas hybridcomponent of this resonant transfer acceptor CO arrangement consists ofselected mixes comprising one or more of the gases (HI, H¹³CN , He,Argon, I₂, H₂, CO) in appropriate combination for the desired operationand configured for closed cycle functioning and limited chemicalreaction recovery as required.
 18. An optically pumped molecular lasersystem according to claim 14, wherein the solid state pump componentconsists of one or more laser diode pumped solid state masteroscillators, tuned and locked onto desired gas overtone transition(s)with combination of these outputs by spectral beam combination or anyother suitable technique followed by introduction of this commonmultispectral source beam into a laser diode pumped solid stateamplifier to generate pump powers (irradiances) consistent with theobjective of driving the gas into a saturation condition consistent withonset and maintenance of a full to ground return sustained fundamentalor other transition lasing cascade (FIG. 1).
 19. An optically pumpedmolecular laser system according to claim 14, wherein the gas componentif appropriately configured and pumped will lase on donor and donor andacceptor transitions—or preferentially on acceptor only.
 20. Anoptically pumped molecular laser system according to claim 14, whereinintra gas component cavity low gain cell(s), of at least ¹²CO₂+¹³CO₂ (orany other suitable molecular component of suitably defined spectralabsorption) at several hundred Torr each in an atomic or homonuclearmolecular buffer gas of several atmospheres, will channel lasing intoatmospheric windows with efficiency if required.